1. Field of the Invention
Illustrative aspects of the present invention relates to techniques of reading images on a duplex document by scanning the document, and more particularly to techniques of varying at least one of start-of-reading timings with which an image reader starts reading opposite sides of a duplex document, respectively.
2. Description of the Related Art
In the industries of image forming apparatuses which are typically copiers or the like, there are known image reading apparatuses which incorporate an Auto Document Feeder (ADF) for feeding a document from a supply tray (i.e., an input tray) to an exit tray (i.e., an output tray) via a transport path (i.e., a feed path).
As one of various types of the above image reading apparatuses, there is known an image reading apparatus for reading a document for duplex purposes by scanning the document. This type of image reading apparatus is adapted to read the images previously formed on opposite sides (i.e., a first side and a second side) of a document during one cycle of document scanning operation.
In the automatic document feeder of JP-A-8-133551 discloses a type of image reading apparatus in which a document to be read is transported in a so-called switch-back manner that the original trailing end of the document is changed to the new leading end of the document for enabling duplex reading of the document.
FIGS. 19 and 20 illustrate a transport path employed in an image reading apparatus of the prior art, which can combine an ADF having a duplex reading function.
As illustrated in FIG. 19, a document G placed on a supply tray 100 with its first side facing upwardly is fed to a transport path 102 by a supply roller 101. The document G is transported along the transport path 102 so as to reach and pass through feed rollers 103 provided as desired.
As the document G moves across a scanning position X, the first side of the document G is read by an image reader 107 such as a CCD or a CIS. When the document G having its first side read is detected at its trailing end by a suitable sensor (not shown), exit rollers 104 are stopped while nipping the trailing end the document G.
As illustrated in FIG. 20, the exit rollers 104 reverse the transfer direction of the nipped document to a bi-directional path 105. The document G is then transferred again from the bi-directional path 105 to the transport path 102 to the upstream side of the scanning position X of the transport path 102. Consequently, the original leading end and the trailing end of the document G are reversed.
Then, the document G, which is fed forward by the feed rollers 103, moves across the scanning position X, while the image reader 107 reads a second side (opposite to the first side) of the document G.
When the document G having its second side read is detected at its trailing end by a suitable sensor (now shown), the exit rollers 104 are stopped while nipping the trailing end of the document G, and subsequently, the exit rollers 104 reverse the transfer direction of the nipped document to the bi-directional path 105.
The document G which has entered the transport path 102 from the bi-directional path 105 is Drought into a state in which the original trailing end of the document has been reversed to the new leading end of the document G, which is to say, a state in which the first side of the document G faces the scanning position X.
Then, the document G is fed forward along the transport path 102 to the exit tray 106 with the first side facing downwardly.
As a result of the above operation, the document G is read for a duplex mode to read both the first and second sides of the document G. Further, when the document G was one of documents stacked in the supply tray 100 in an original sequence, the document G is delivered to the exit tray 106 and placed on other documents previously placed on the exit tray 106 in the same sequence as the original one.
When an image recording apparatus incorporating the above-described image reading apparatus is used for duplex reading of an A4-sized document 110 having opposite sides on which respective images have been printed as illustrated in FIGS. 21(a) and 21(b), limitations can result as described below.
FIG. 21(a) illustrates a first side of the document 110 on which an image of “ABC” has been drawn along one of opposite short edges of the document 110, while FIG. 21(b) illustrates a second side (opposite to the first side) of the document 110 on which an image of “abc” has been drawn along one of the opposite short edges of the document 110.
The document 110 is categorized as a document bound along one of opposite long edges of the document for creation of files, books, booklets, flipbooks, calendars, for example.
That is to say, for the thus-categorized document 110, the image of “ABC” has been drawn on the first side of the document 110, on the basis of the fact that a long edge 111 is one of opposite long edges of the document 110 along which the document 110 will be bound, which is to say, using as a reference for image disposition, the long edge 111 along which the document 110 is to be bound for filing.
On the other hand, the image of “abc” has been drawn on the second side of the document 110, on the basis of the fact that a long edge 112 is one of opposite long edges of the document 110 along which the document 110 will not be bound, which is to say, using as a reference for image disposition, the long edge 112 along which the document 110 is not to be bound.
FIGS. 22(a) and 22(b) illustrate how the document 110 is transported in portrait or vertical orientation, and FIGS. 23(a) and 23(b) illustrate image data representative of the images on the document 110 which have been read by the image reader 107.
In FIGS. 21 and 23, the white arrows indicate the directions in which the opposite sides of the document 110 are read by the image reader 107 along the opposite sides.
For clarification of a document orientation in which a length of the document 110 is oriented with respect to a transport direction of the document 110, a top edge of the document 110 when viewed in a direction to allow an image formed on each side of the document 110 to erect is colored black to form a black-colored band.
Hereinafter, the top edge of a document will be referred to as “image-based top edge,” while an opposite edge of the document, which is to say, a bottom edge of the document when viewed in a direction to allow the image formed on the document to erect will be referred to as “image-based bottom edge.”
As illustrated in FIG. 22(a), when the document 110, which is to be bound along its one long edge, is transported with its first side facing upwardly, and with its image-based top edge (i.e., one of short edges of the document 110) leading in the transport direction of the document 110 (i.e., in portrait orientation), the image reader 107 starts reading the image on the first side of the document 110 at its image-based top edge.
FIG. 23(a) illustrates image data 113 produced by reading the first side of the document 110. After the image reader 107 finishes reading the first side of the document 110, the transport direction of the document 110 is reversed using a bi-directional path (not shown), to thereby change the original trailing end to the new leading edge of the document 110.
That is to say, the position of the image-based top edge and the position of the image-based bottom edge are switched to each other, with the result that the image-based bottom edge becomes the new leading edge.
Subsequently, the document 110 returns to an original transport path, and eventually, the image reader 107 starts reading the image on the second side of the document 110 at its image-based bottom edge. FIG. 23(b) illustrates image data 114 produced by reading the second side of the document 110.
There exists a case where the produced sets of image data 113 and 114 are enlargement printed using an image enlargement/reduction function provided in the image recording apparatus.
In this case, enlargement processing is performed for both the sets of the image data 113 and 114, using one of two extremes (i.e., opposite end points) of a start-of-reading edge of each of images represented by the sets of image data 113 and 114, or otherwise a center point 117 of the start-of-reading edge, as a reference point for enlargement.
In FIGS. 24(a) and 24(b), there are illustrated sets of enlargement image data 115 and 116 of the first and second sides of the document 110, the enlargement image data 115 and 116 being produced by the above-described enlargement processing at a desired magnification ratio (>100%) using the center point 117 of the above-described start-of-reading edge of the original image data 113 and 114 as the reference point for enlargement.
In FIGS. 24(a) and 24(b), there are illustrated the thus-produced enlargement image data 115 and 116 in solid lines, together with the size of the original document 110 (equal to the size of the original image data 113 and 114 illustrated in broken lines), for the convenience of comparison in size between the enlargement image data 115 and 116 and the A4-sized document 110.
Now, it is assumed that the size of the enlargement image data 115 and 116 is larger than the size of a recording sheet of paper or a print sheet (assuming that the recording sheet has the same size as the A4-sized document 110, in this instance).
In this instance, prior to the print of the enlargement image data 115 and 116 of the first and second sides of the document 110, the enlargement image data 115 and 116 are temporarily stored in an image memory.
For the first side of the document 110, the corresponding enlargement image data 115 has been produced as a result of the image reader 107 starting reading the first side of the document 110 at its image-based top edge. In this instance, the start-of-reading edge is equal to the image-based top edge.
Therefore, if the apparatus stores in the image memory only a portion of the enlargement image data 115 which ranges from a start edge of the enlargement image data 115 to a position distant from the start edge by a length equal to the longitudinal length of the recording sheet, and if the apparatus subsequently prints out the enlargement image data 115, then the enlargement print of the document 110 will be performed successfully, without any additional processing including such as processing of reversing the order of the image data.
On the other hand, for the second side of the document 110, the corresponding enlargement image data 116 has been produced as a result of the image reader 107 starting reading the second side at its image-based bottom edge. In this instance, the start-of-reading edge is equal to the image-based bottom edge.
Therefore, for and prior to successful print of the enlargement image data 116, the entire enlargement image data 116 is needed to be stored tentatively in the image memory, and to then perform additional processing including processing of trimming the enlargement image data 116 to a desired print region 118 (illustrated in FIG. 24(b) in dash-dot-dot lines), and processing of reversing the order of the trimmed image data for collating the image data of the first and second sides of the document 110.
For the above reasons, such an image recording apparatus that is configured to start reading a second side of a document at its image-based bottom edge can present a problem that an image memory requires an increased capacity adequate to store pre-processed enlargement image data.
Japanese Patent Application Publication No. 2002-125102 discloses an image forming apparatus allowing a start-of-reading position on a document to be read by an image reader, to be deviated from its original position as a function of a size ratio of a recording sheet to the document and an enlargement/reduction ratio for copying.